The retreatment of tailings storage facilities (TSFs) is emerging as one of the mining industry’s most compelling opportunities to unlock value while addressing legacy environmental risks.

According to Danie Otto, Asset Transition and Closure Business Lead at SLR Consulting, the opportunity is being driven by significant shifts in the scale, technology and regulatory context surrounding tailings management. Otto, who is also President of the Land Rehabilitation Society of Southern Africa, says retreatment enables a fundamental reset in environmental compliance.

“When historic tailings are reprocessed and relocated, they must be deposited in facilities designed to meet modern regulatory requirements, including the Global Industry Standard on Tailings Management,” he explains. “This represents a step change from older TSFs which were established under far less stringent standards.”

Modern facilities can now be designed, constructed and managed using today’s professional expertise and the latest pollution control technologies. These include engineered liners, drainage systems and water recovery infrastructure that significantly reduce seepage risks.

“In effect, retreatment allows companies to upgrade their legacy environmental risks into assets that comply with current best practice,” Otto says. “This is something that would be far more difficult to achieve in situ with an old TSF.”

While TSF retreatment remains strongly driven by economics, many historic dumps still contain valuable recoverable minerals. Gold, in particular, has become increasingly attractive as commodity prices have strengthened. However, the financial upside extends well beyond mineral recovery.

“By removing legacy deposits and relocating material to modern facilities, mining companies can significantly reduce long-term environmental liabilities,” he says. “This reduces the liability of continuous seepage treatment and continuous dust prevention, for instance, as these features are more efficiently built into the new systems.”

Advances in technology are further supporting this transition. Otto highlights developments in geosynthetic materials and liners as one of the most important innovations shaping modern TSFs.

“An important field of development is in geosynthetic materials and liners which form the backbone of pollution control in modern TSFs,” he says. “These systems prevent contamination by capturing and recycling seepage from the TSF, preventing it from infiltrating the surrounding environment.”

At the same time, erosion control technologies such as biodegradable netting are transforming rehabilitation efforts. These nets reduce wind force, minimise dust pollution and create more favourable conditions for vegetation to establish and thrive. Because they are made from organic materials, they biodegrade over time and contribute positively to the surrounding ecosystem.

“On the biological front, innovations in phytoremediation and microbiology are pushing the boundaries even further,” Otto continues. “Scientists are now able to deploy bacteria and plants that actively neutralise pollutants, absorb heavy metals and improve soil conditions.”

Using bacteria that consume acid, professional scientists have been able to extract sulphates and generate carbonates from TSFs, effectively producing alkaline conditions from acidic environments. Similarly, certain plant species act as hyper-accumulators, drawing contaminants from tailings and storing them in biomass that can then be removed from the system.

“While it is difficult to render tailings completely inert, these technologies significantly reduce environmental risk and improve ecological outcomes,” he says.

Beyond containment and remediation, modern TSF strategies are also aligning with broader sustainability goals such as biodiversity restoration and carbon sequestration.

“Relocating tailings and creating new storage facilities opens the door to modern interventions that support vegetation growth, prevent erosion and encourage ecological succession,” Otto explains. “This makes it more viable to gradually transform engineered landscapes into functioning ecosystems.”

In some cases, these efforts may also generate additional revenue streams through carbon and biodiversity credits, further strengthening the commercial case for rehabilitation.

Despite ongoing challenges around compliant mine closure - particularly mine closure certification - Otto emphasises that TSF retreatment remains one of the most practical and impactful pathways for addressing mining’s environmental legacy.

“By combining economic incentives with technological innovation and stricter regulatory frameworks, retreatment offers a rare alignment of interests between industry, regulators and society,” he concludes.